Osstell Resonance Frequency Measurement Values as a Prognostic Factor in Implant Dentistry.

Resonance frequency analysis (RFA) using the Osstell device (Osstell AB, Gothenburg, Sweden) has been advocated for quantifying implant stability on a relative scale of implant stability quotients (ISQ). It was the goal of this prospective clinical study to evaluate whether a certain ISQ level, at the time an implant is placed, correlates with successful osseointegration as some have claimed. Four hundred ninety-five implants (Straumann AG, Basel, Switzerland), varying in length and diameter, were placed in a private practice, strictly adhering to the implant manufacturer's surgical protocol. After placement and after healing periods of 42 days in the mandible and 56 days (implant manufacturer's protocol) in the maxilla, implant stability was measured using RFA. After healing, implants were torqued forward at 35 Ncm and allowed to heal further if the patients felt discomfort. Statistical analysis of the data obtained was based on Welch tests and Kolmogorov-Smirnow tests (level of significance α = 0.05). Results showed that 432 implants were osseointegrated after the predefined healing periods while 8 implants were lost and, in 55 cases, healing was prolonged. Both at insertion (P = .025) and after healing (P < .001), successful implants showed significantly different ISQ values as compared to implant failures or implants with prolonged healing. However, overlapping ISQ distributions at implant insertion demonstrated that there was no correlation among the data that could be used to predict successful osseointegration. Within the limits of this study, the prognostic value of ISQ values appears to be ambiguous.

Effect of various fixation parameters on strain development of screw- and cement-retained implant-supported restorations.

OBJECTIVE: The objective of this study was to quantify the potential effects of screw- and cement-retention on strain development of implant-supported fixed dental prostheses (FDPs). METHOD AND MATERIALS: A total of 20 single crowns and 70 three-unit FDPs were fabricated to fit an in vitro model situation with two implants. Using strain gauges attached to the model material adjacent to the implants, strain development of the restorations during fixation was recorded while the parameters cement type (provisional and definitive cement), cementation force (10 N and 100 N), and tightening torque (5 Ncm, 10 Ncm, and 15 Ncm) were varied. MANOVA with Pillai's trace was used for pairwise comparisons between groups (α = .05). RESULTS: Mean absolute strain development ranged from 5.11 µm/m for to 27.26 µm/m for single crowns and from 16.46 µm/m to 689.04 µm/m for multi-unit restorations. Screw-retained single crowns exhibited significantly smaller strain development as compared to cement-retained single crowns (P = .009). The type of cement used seemed to have no effect on strain development of an FDP regardless of the cementation force applied (P = .064 and P = .605). An increase in tightening torque for screw-retained FDPs also had no effect on resulting strain development (P values ranging from .692 to .807). Nonuniform results were found when comparing screw- and cementretention as the retention mechanism for FDPs. CONCLUSION: Strain development seems to depend predominantly on the accuracy achieved during the fabrication process whereas the retention mechanisms themselves as well as their potential parameters only have a minor effect.

Effect of rotating osteotomes on primary implant stability-an in vitro investigation.

Achieving sufficient primary implant stability in poor-quality bone is difficult. Other than for conventional osteotomes, little is known about the effectiveness of screw-shaped spreaders in condensing bone and increasing primary stability. Therefore, implant stability quotient (ISQ) measurements of implants placed in bone surrogate models were conducted. Whereas bony microarchitecture had no effect on implant stability, initial bone density, presence of a cortical layer, and the use of screw-shaped spreaders significantly increased ISQ levels.

Effect of intraoral scanning on the passivity of fit of implant-supported fixed dental prostheses.

OBJECTIVES: Passive fit between restorations and implants is considered a significant factor in preventing mechanical and biologic failures in implant dentistry. Since impression taking and master cast fabrication have been shown to cause substantial errors, it was the aim of this study to evaluate the effect of intraoral scanning on the passivity of fit of three-unit cement-retained implant-supported fixed dental prostheses (FDPs). METHOD AND MATERIALS: Conventional and optical impressions (n = 10) of an in vitro situation with two implants in the mandibular left quadrant were made. Based on the scans, 10 FDP frameworks were CAD/CAM fabricated from zirconia ceramic; stereolithographic casts were also made. On both the stereolithographic casts and the casts obtained from the conventional impressions, 10 frameworks were waxed and cast in dental training alloy. Subsequently, all samples were cemented on the in vitro model, while the strains emerging were recorded for statistical analysis (MANOVA with Pillai trace; ß = .05). RESULTS: The restorations fabricated on the stereolithographic casts showed significantly lower levels of strain than the conventionally fabricated ones (P = .013). No significant difference could be found between conventionally and CAD/CAM-fabricated frameworks (P = .080). CONCLUSION: Intraoral digitization of dental implants appears to be at least as precise as conventional impression taking and master cast fabrication using prefabricated transfer components and laboratory analogs.

Microfractures in metal-ceramic and all-ceramic implant-supported fixed dental prostheses caused by superstructure fixation.

The effect of ceramic veneering on the passivity of fit of cast metal and CAD/CAM-fabricated zirconia ceramic implant-supported three-unit cement-retained restorations was investigated, as well as the effect of misfit stress on the marginal integrity of ceramic veneers. Superstructures were fabricated using cast metal or by CAD/CAM milling of presintered or HIP zirconia ceramic (n=10). Before and after veneering, strain gages were used to measure in vitro the strain developed in all the restorations as a result of superstructure fixation. Fluorescent penetrant method was used to detect microcracks developed in ceramic veneers. Cast frameworks showed significantly higher strain values than CAD/CAM frameworks (p=0.000). Veneering significantly increased strain development in all CAD/CAM frameworks (p=0.000). Compared to zirconia ceramic restorations, significantly more microcracks were observed in cast restorations (p=0.000) both before and after superstructure fixation.

Passivity of fit of CAD/CAM and copy-milled frameworks, veneered frameworks, and anatomically contoured, zirconia ceramic, implant-supported fixed prostheses.

STATEMENT OF PROBLEM: There is less information on the quality of fit of zirconia frameworks with or without ceramic veneer than on anatomically contoured milled zirconia restorations. PURPOSE: The purpose of this in vitro study was to evaluate the strain development of CAD/CAM fabricated zirconia ceramic frameworks with and without ceramic veneering, copy-milled zirconia ceramic frameworks, and copy-milled zirconia ceramic anatomic contour restorations. MATERIAL AND METHODS: Four groups of 3-unit implant-supported cement-retained restorations were fabricated (n=10) to fit an in vitro model with 2 implants. Strain gauges which recorded the strain development of all restorations during cementation were attached to the model mesially and distally adjacent to the implants. Mean absolute strain values were recorded for statistical analysis (MANOVA with Pillai's trace; α=.05). RESULTS: Mean absolute strain development at the different strain gauge locations ranged from 83.23 µm/m for copy-milled zirconia ceramic anatomic contour restorations to 301.20 µm/m for veneered CAD/CAM fabricated zirconia ceramic restorations. Significant effects (P<.001) of the fixed factors restoration type and veneering status, as well as of their interaction term (P=.001) were found. Ceramic veneering of CAD/CAM frameworks resulted in higher strain development, whereas the greater volume in copy-milled anatomic contour restorations did not affect accuracy. CONCLUSIONS: With the systems used in this study, zirconia ceramic-based anatomic contour restorations show greater passivity of fit than ceramic veneered CAD/CAM fabricated zirconia ceramic frameworks.

Strain development of implant-supported fixed prostheses copy milled from zirconia ceramic.

The aim of this research was to quantify the strain development of three-unit implant-supported fixed partial dentures (ISFPDs) copy milled from zirconia ceramic. Three ISFPD groups (n = 10) were fabricated by means of casting, copy milling, and computer-aided design/computer-assisted manufacturing (CAD/CAM) to fit an in vitro model with two implants. During cementation of the restorations, the emerging strains were recorded using strain gauges attached to the cast material mesially and distally adjacent to the implants. Absolute mean strain development ranged from 85.39 Μm/m to 326.83 Μm/m at the different strain gauge locations. Fabrication method had a significant effect on strain development (multivariate analysis of variance, P = .011), with the cast restorations showing the highest strain development and the CAD/CAM-fabricated ISFPDs showing the lowest. Copy milling leads to ISFPs that are more precise than cast restorations but less precise than CAD/CAM-fabricated restorations.

Sensitivity of transillumination for detecting microcracks in feldspathic and zirconia ceramic materials.

STATEMENT OF PROBLEM: Despite good clinical success rates of ceramic restorations, fractures of substructures made from high-strength dental ceramics remain an issue. Transillumination of ceramic restorations has been proposed as a means of quality assurance. PURPOSE: The purpose of this study was to compare the sensitivity of transillumination and the fluorescent penetrant method (FPM) in detecting microcracks in zirconia and feldspathic ceramic materials. MATERIAL AND METHODS: Two groups (n=20) of standardized plates were fabricated from zirconia ceramic (Cercon) and feldspathic ceramic (VITABLOCS Mark II for CEREC) materials, and central holes were created to induce microcracks. The plates were microscopically analyzed at ×20 magnification by means of transillumination and FPM. Based on whether the criterion crack was recognized or not recognized, contingency tables were developed. Fisher's exact test for count data was used to compare frequency distributions (α=.05). RESULTS: Minimum crack length as detected by FPM was 18 µm in zirconia ceramic and 17 µm in feldspathic ceramic. For transillumination, minimum detectable crack length was 54 µm in zirconia ceramic and 33 µm in feldspathic ceramic. Thirty-seven percent of cracks in feldspathic ceramic plates and 64% of cracks in zirconia ceramic plates could not be detected by means of transillumination. The conditional probabilities for a crack being detected by transillumination, although it was detected by FPM, were significantly lower than 1 for both materials (P<.001). Although transillumination was less sensitive than FPM on a relative scale, it was not possible to demonstrate a general difference between the 2 analyzing techniques by using statistical methods. CONCLUSIONS: Using FPM as a relative reference system, transillumination appears to be less sensitive in detecting microcracks in ceramic components.

In vitro fracture resistance of copy-milled zirconia ceramic posts.

STATEMENT OF PROBLEM: Current copy-milling systems allow for the fabrication of 1-piece zirconia ceramic posts and cores, which can be used in combination with ceramic crowns to restore endodontically treated teeth in an esthetic manner. However, limited data are available on the fracture resistance of copy-milled zirconia ceramic posts. PURPOSE: The purpose of this in vitro study was to compare the fracture resistance of prefabricated posts made from zirconia ceramic and fiber-reinforced composite resin with the fracture resistance of copy-milled zirconia ceramic posts. MATERIAL AND METHODS: Three groups of posts and cores were fabricated (n=10): prefabricated zirconia ceramic posts with composite resin cores (ZIR), fiber-reinforced composite resin posts with composite resin cores (FRC), and copy-milled zirconia ceramic posts and cores (CM). Following artificial aging by thermal cycling and masticatory simulation, compressive tests were performed in a universal testing machine with the posts mounted at an angle of 135 degrees to the long axis of the posts. The maximum forces needed to fracture the posts were recorded for statistical analysis (1-way ANOVA, Tukey's Honestly Significant Difference test; alpha=.05). RESULTS: The mean maximum forces (SD) needed to fracture the posts and cores were 123.10 (19.38) N for FRC, 139.30 (42.70) N for CM, and 267.10 (59.11) N for ZIR. The prefabricated zirconia ceramic posts required significantly higher fracture loads as compared to FRC (P<.001) and CM (P<.001). CONCLUSIONS: The fracture load of copy-milled zirconia ceramic posts is significantly lower than that of prefabricated zirconia ceramic posts of the same size.

A methodology to study the effects of prosthesis misfit over time: an in vivo model.

PURPOSE: Passive fit of implant-supported superstructures cannot currently be achieved. The aim of this investigation was to create a methodology that can be used to study the effects of prosthesis misfit in humans. MATERIALS AND METHODS: An edentulous patient received two interforaminal implants and a screw-retained bar for the retention of the mandibular denture. A corresponding in vitro model with strain gauges placed mesially and distally, adjacent to the implants, was fabricated to serve as a standardizing control. Over a period of 6 months, a total of 10 measurements on both the in vitro model and in the patient's mouth were conducted with newly fixed strain gauges on the bar. RESULTS: The in vitro experiments showed that no component wear at the abutment-bar interface had occurred and that repositioning of the strain gauges on the bar caused deviations in strain measurements up to 10.55%. In vivo, a reduction in strain development, from 445 to 383 Mum/m, was observed in the initial phase up to 12 weeks after bar insertion. Subsequently, the measurement values increased, and after a period of 24 weeks, they nearly reached the initial strain level (443 microm/m). Only minor changes in strain development of the bar could be detected; these might be a result of limited dynamic loading and the cortical architecture of the surrounding bone. Deviations in measurement accuracy caused by repositioning of the bar strain gauge are a limitation of this technique and should be eliminated in future studies. CONCLUSIONS: The present methodology can be applied to study changes in static implant loading over time in humans.

Stability of screw-retained implant-supported fixed dental prostheses bonded to gold cylinders.

This study examined the adhesive stability of screw-retained implant-supported fixed dental prostheses (FDPs) bonded to prefabricated gold cylinders after a load cycling. Five FDP groups (n = 10 per group) that differed either in bonding or loading modality (no loading, loading, moment loading, humidity, silicoating) were compared based on the forces needed to separate the FDP frameworks from the gold cylinders. The mean separating forces for the different groups ranged from 311 N to 501 N. No statistically significant differences could be detected between the five groups (Welch t test, P = .447). Despite the limited transferability into clinical practice, it appears that sufficient bonding stability can be achieved for screw-retained implant-supported FDPs bonded to prefabricated gold cylinders.

The effect of load cycling on metal ceramic screw-retained implant restorations with unrestored and restored screw access holes.

STATEMENT OF PROBLEM: It has been shown that under cyclic loading, more chipping fractures of the veneer ceramic occur on the occlusal surface of screw-retained implant-supported fixed partial dentures (FPDs) with unrestored screw access holes (SAHs) than in cemented restorations. This lack of stability may result in esthetic and functional problems. PURPOSE: The purpose of this study was to investigate whether, under dynamic loading, fewer chipping fractures occur on the occlusal surface of screw-retained ceramic veneered implant FPDs with restored SAHs than in those with unrestored SAHs. MATERIAL AND METHODS: Twenty screw-retained ceramic veneered 5-unit FPDs were manufactured for a 3-implant situation and divided into 2 groups of 10 unrestored and 10 SAHs restored with adhesive composite resin restorations (Tetric Evo Ceram). A masticatory simulator was used to load the FPDs occlusal to the implant positions for 20,000 cycles with a force of 100 N applied for 1 second, followed by 1 second of no loading. Three prosthodontists evaluated the FPDs using a light microscope and a dental probe. The number of chipping fractures found were analyzed using a generalized linear model with Poisson response and log link function (alpha =.05). RESULTS: Investigators found significantly more chipping fractures in the group of screw-retained FPDs with unrestored SAHs. The rate ratio of unrestored versus restored prostheses was 3.29 (P=.006). CONCLUSIONS: Adhesive composite resin restorations can significantly reduce the number of chipping fractures occurring around the SAHs of screw-retained implant-supported restorations.

Structural changes in ceramic veneered three-unit implant-supported restorations as a consequence of static and dynamic loading.

OBJECTIVES: Static implant loading caused by non-passive restorations may cause technical complications. As metal-ceramic restorations are most common in implant prosthodontics, the objective of the study was to investigate the effect of static and dynamic loading upon the stability of the ceramic veneer of implant-supported fixed partial dentures (FPDs). METHODS: A total of 10 groups of three-unit implant FPDs with five samples each were investigated in the conditions after fabrication, static loading and dynamic loading (chewing simulator, 20,000 cycles, 100N). The fluorescent penetrant method (FPM) was applied to detect microcracks at the cervical and occlusal aspects of the FPD abutments. Statistical analysis was performed based on the number of microcracks (t-test) and the presence of chipping fractures (Exact Fisher test) with the level of significance set at alpha=0.05. RESULTS: Static and dynamic loading led to an increase both in number of microcracks and frequency of chipping fractures. After static loading, the screw-retained FPDs cast in one piece revealed significantly lower numbers of cervical microcracks than did the cementable restorations fabricated from repositioning technique impressions (p=0.003). The screw-retained FPDs which were fabricated using premachined gold cylinders showed the highest numbers of cracks and chipping fractures both after static and dynamic loading. SIGNIFICANCE: Static loading may damage the ceramic layer of implant-supported restorations. The use of prefabricated components may cause increased numbers of microcracks due to the lack of bonding oxides.

Influence of fixation mode and superstructure span upon strain development of implant fixed partial dentures.

PURPOSE: Implant-borne fixed partial dentures (FPDs) should fit passively in order to avoid complications ranging from screw loosening to loss of osseointegration. The aim of this study was to measure the strain development of three-unit and five-unit screw- and cement-retained implant-supported FPDs. Additionally, the influence of the parameters retention mechanism and FPD span were evaluated. MATERIALS AND METHODS: Three Straumann implants were anchored in a measurement model based on a real-life patient situation and strain gauges (SGs) were fixed mesially and distally adjacent to the implants and on the pontics of the superstructures. During cement setting and screw fixation of 40 implant FPDs (10 samples from each group: three-unit cementable; five-unit cementable; three-unit screw-retained; five-unit screw-retained), strain development was recorded. For statistical analysis, multivariate two-sample tests were performed with the level of significance set at p= 0.1. RESULTS: The mean strain values for the four FPD groups at the different SG sites ranged from 26.0 to 637.6 microm/m. When comparing the four groups, no significant differences in strain magnitude could be detected. Similarly, a comparison of the two FPD spans revealed no significant difference (p= 0.18 for cementable FPDs; p= 0.22 for screw-retained FPDs). A comparison of the two fixation modes also revealed no significant difference (p= 0.67 for three-unit FPDs; p= 0.25 for five-unit FPDs). CONCLUSION: FPD span and retention mechanism appear to have only a minor influence on strain development in implant FPDs. As implant-supported restorations have proven to be successful over time, the question arises as to whether an "absolute" passive fit is a prerequisite for successful implant restorations.

Parameters of resonance frequency measurement values: a retrospective study of 385 ITI dental implants.

OBJECTIVES: There is no proven clinical tool to evaluate the amount of osseointegration and stability around dental implants. Therefore, the aim of this retrospective clinical study was to evaluate resonance frequency analysis values of 385 ITI solid screw implants. MATERIAL AND METHODS: Both at implant placement and after healing, implant stability quotients (ISQs) were determined. For statistical analysis, Pearson's correlation coefficients, Welch's two-sample t-tests and paired samples t-tests were computed at a level of significance of alpha=0.05. RESULTS: ISQ values ranged from 39 to 86 at implant placement and from 35 to 89 after healing, showing a significant increase. The highest ISQ values at both stages were obtained in the posterior mandible (P < or = 0.002). After healing, ISQ values in the anterior mandible were significantly higher than in the anterior maxilla (P=0.005). Implant length had a significant influence on ISQ in the anterior mandible (P=0) at insertion and in the anterior (P=0.005) and posterior mandible (P=0.036) after healing. Implant diameter and ISQ at insertion correlated in the anterior mandible (P=0.037). After healing, a significant influence was found for all regions, except the posterior maxilla (P=0.795). With the exception of the anterior maxilla (P=0.542), ISQ at placement had a significant influence on ISQ after healing. In the anterior maxilla (P=0.002) and in the posterior mandible (P=0.007), healing time significantly influenced ISQ after healing. CONCLUSIONS: It appears that only repeated ISQ measurements of a specific implant have some diagnostic benefit, although the parameters influencing the absolute values still remain unclear.

In vitro effect of load cycling on metal-ceramic cement- and screw-retained implant restorations.

STATEMENT OF PROBLEM: In implant prosthodontics, restorations can either be cement- or screw-retained. Aside from passivity of fit, esthetics, and retrievability, the occlusal opening of the screw-access hole (SAH) is a major difference between the 2 types of restorations. In veneered fixed partial dentures (FPDs), the SAH forms a discontinuity of the ceramic layer and may be an origin for chipping fractures. PURPOSE: The objective of this study was to investigate whether more chipping fractures occur during dynamic loading on the occlusal surface of screw-retained ceramic-veneered implant FPDs than in cement-retained restorations. MATERIAL AND METHODS: Ten cement-retained and 10 screw-retained ceramic veneered 5-unit FPDs were manufactured for a 3-implant situation. A masticatory simulator was used for loading the occlusal surface of the FPDs to the implant positions for 20,000 cycles with a force of 100 N applied for 1 second followed by 1 second of no loading. For analysis, 3 clinicians evaluated the FPDs using a light microscope and a dental probe. The numbers of chipping fractures found were analyzed by means of a generalized linear model with Poisson response (alpha=.05). RESULTS: The investigators found significantly more chipping fractures in the group of screw-retained FPDs, the rate ratio of screw-retained FPDs versus cement-retained FPDs being greater than 1 with a P value of .0023. CONCLUSION: The SAH of screw-retained implant FPDs forms a weak point of the ceramic layer.

Loading of bone surrounding implants through three-unit fixed partial denture fixation: a finite-element analysis based on in vitro and in vivo strain measurements.

Implant-borne fixed partial dentures (FPDs), whether cementable or screwable superstructures, ought to display a true passive fit. The objective of this in vivo-based finite-element analysis is, therefore, to quantify the degree of stress which occurs in the bone around the implants as a result of the fixation of cemented and screw-retained FPDs. On the basis of a simulated patient situation with two implants, six groups of implant-supported superstructures containing 10 samples each were fabricated. Strain gauges which were mounted on the pontics of the restorations were subsequently used to take in vivo measurements (Ethics Commission Approval No. 2315). Taking the values obtained as a basis, the von Mises equivalent stress was chosen to illustrate bone loading in three-dimensional finite-element models. Superstructure fixation caused residual interface stress as high as 30 MPa. Similar stress magnitudes can be observed for axial implant loading of 200 N. Assuming that the axial loading of a single implant with 200 N is within the bone's physiological range, it can be concluded that the degree of stress resulting from the fixation of superstructures alone does not constitute a risk.

Strain situation after fixation of three-unit ceramic veneered implant superstructures.

The passive fit of superstructures used in implant prosthodontics is affected by several variables. The objective of this study was to quantify the strain development in various fixed partial dentures (FPDs), both in the condition as cast and after ceramic veneering. Five different types of three-unit FPDs (cementable/repositioning technique impression; cementable/pick-up technique impression; screw-retained/plastic cylinder; screw-retained/gold cylinder; screw-retained/bonded) with 10 samples each, representing commonly used FPD-types, were investigated before and after ceramic veneering. Two ITI implants were anchored in a measurement model simulating a real-life patient situation and strain gauges were mounted close to the implants. The strain development was recorded during cement setting and screw fixation. For statistical analysis, multivariate two-sample tests were performed with the level of significance set at P = 0.1. All FPDs revealed measurable amounts of strain. Neither the impression technique nor the fabrication modes for conventional screw-retained FPDs had a significant influence on strain development. Ceramic veneering caused an increase in strain development for the conventional bridge types. Furthermore, cementing appears to be able to compensate fabrication inaccuracies better than screw retention. The lowest strains were found in FPDs bonded to gold cylinders on the measurement model for metal frames and ceramic-veneered FPDs. Conventional procedures are unable to produce superstructures with an absolute passive fit. The technique of bonding superstructures to prefabricated components in the oral cavity seems to compensate for various shortcomings in superstructure fabrication.

Static implant loading caused by as-cast metal and ceramic-veneered superstructures.

STATEMENT OF PROBLEM: The passive fit of superstructures for implant-supported restorations is affected by each step of the fabrication process. In this context the question arises whether ceramic veneering would increase static implant loading. PURPOSE: The purpose of this study was to quantify the strain development of various fixed partial dentures (FPDs) both in the as-cast condition and after ceramic veneering. MATERIAL AND METHODS: Four different types (n = 10) of 5-unit FPDs (cementable, screw retained/plastic cylinder, screw retained/gold cylinder, screw retained/cemented) representing commonly used types of FPDs were investigated before and after ceramic veneering. Three implants were placed in a model simulating a patient situation, and strain gauges were mounted mesially and distally adjacent to the implants. The strain development was recorded during cement setting (provisional cement) and screw fixation. The data were analyzed statistically using multivariate 2-sample tests (alpha=.1). RESULTS: All FPDs revealed measurable amounts of strain. Neither the type of retention nor the mode of fabrication for conventional screw-retained FPDs had a significant influence on strain development. Ceramic veneering caused an increase in strain development for the conventional fixed partial dentures tested. The lowest strains were found in FPDs cemented to gold cylinders on the model for the metal frames and the ceramic-veneered FPDs. CONCLUSION: Conventional procedures were unable to produce superstructures with absolute passive fit. Ceramic veneering appeared to increase strain development and, thus, inaccuracy of the fit. The technique of cementing superstructures to prefabricated components directly on the implants may compensate for dimensional errors caused by impression making and superstructure fabrication.

Mandibular two-implant telescopic overdentures.

To stabilize mandibular overdentures in edentulous patients, various connector types which can be attached to between two and four implants placed in the anterior mandible are possible. Treatment using non-rigid telescopic connectors on two interforaminal implants for overdenture stabilization began in 1989. The objective of this study is to investigate soft- and hard-tissue conditions as well as prosthesis function after a period of 10 years. This also involved an evaluation of correlations between radiographic and clinical parameters. Twenty-three subjects with 46 interforaminal implants (ITI solid screw implants, 12 mm in length, 4.1 mm in diameter; 10.4 years in situ, range, 8-12.8 years) were investigated. Modified plaque index (mPI), sulcus fluid flow rate (SFFR), modified sulcus bleeding index (mBI), probing depth (PD), distance from implant crown margin to the coronal border of the peri-implant mucosa (DIM), attachment level (AL), width of keratinized mucosa (KM), Periotest values (PTVs) and prosthesis function were evaluated. In the radiographic evaluation, the distance between implant shoulder and first crestal bone-implant contact (DIB) in mm and the horizontal bone loss (HBL) in mm were measured. The relatively high mPI scores (mean, 0.82; score, 0 in 44.4%; SD, 0.83) did not result in increased SFFR scores (mean, 12; min, 3, max, 38; SD, 7.43) or higher mBI scores (mean, 0.35; score, 0 in 70.8%; SD, 0.59), which was commensurate with healthy peri-implant mucosa. A mean PD value of 2.15 mm (min, 1 mm; max, 5 mm; SD, 0.96) and a mean DIM value of 0.28 mm (min, 0 mm; max, 2 mm; SD, 0.52) were measured. The implants were stable, showing a mean Periotest value of -1.91 (max, 02, min, -6; SD, 1.76). A mean DIB of 3.19+/-0.95 mm (range, 1.3-5.16 mm) and a mean HBL of 1.6+/-1.52 mm (range, 0.28-8.33 mm) were calculated. A correlation was found between DIB and the parameters SFFR (P=0.060), DIM (P=0.042), AL (P=0.050) and especially PTV (P<0.01), leading to the assumption that these clinical parameters may be useful indicators of peri-implant bone loss. The results of the 10-year follow-up examination show that non-rigid telescopic connectors with two interforaminal implants for overdenture stabilization appear to be an efficient and effective long-term treatment modality in severely resorbed edentulous mandibles. Particularly in geriatric patient treatment this concept may provide advantages in terms of handling, cleaning and long-term satisfaction.